Hello everyone, Sorry If someone has posted this already. Gary was asking about my avatar picture showing a midicap on a No. 12 stove. I thought I would take some pictures of it in action. The standard burner plate in picture below. The Midicap in place. When the stove is at max and pumped about 30 40 times the midicap is slightly overpowered. As seen in the pictures below. The stove at max power. Below is a shot of the stove throttled back. It can simmer as well. The midicap is slightly overpowered but keeps up and still does an great job. Not bad at all for a cap made and designed for stoves with half the btu output of this stove. Not to mention the tank pressure. Take a bow Gary! The No. 12 being able to maintain high tank pressure and vaporize fuel very well make this a heck of a stove. The damper does tame this great stove. I believe there is room for improvement. Not to give Gary anymore work. A cap like the OmniDawg would work better I believe. Just thinking sorry. Any thoughts? Cheers, Jeff
Hey Jeff, I don't have any thoughts on the issue, but man, them are some nice pics! That number 12 with the midi is so nice! Thanks! sam
Thanks Sam! I am still not happy with the blue in the pictures. damn digital camera! The lantern doesn't help. All the best, Jeff
Hi Jeff, I am a great fan of Gary's midi-cap....but on a No.96 stove! I had never thought to try it on an Army No.12. Wow! What a versatile cap to handle such a power range, even though you can overwhelm it at the higher pressures of your No.12. When I got my No.12 I fettled it and replaced the jet with a new kero jet from an Op 111. I was surprised when I checked the aperture on the original No.12 jet to find it was less then 0.32mm diameter. My Army No.12 is a very powerful stove, pushing out more power than an Op.111 or Primus No.5R at full throttle, probably due to higher tank pressure, as suggested by John Presscsll. I would love to try an Omni-Dawg or Dragon Tamer on my No.12 but will need to check the relative dimensions of the baseplate of these dampers to see if a fit is possible. I am sure that the No.12 has the vaporising capacity to drive one of these larger "Gary-Caps". Incidentally, the thin brass nut on the pump of the Army No.12 is a real POS, as several CCS Members have commented. I bought a deep socket with 24mm across flats, and managed to shift it without rounding the corners. I made sure the gasket was in good condition, and applied a good coating of copper anti-sieze grease to the threads before re-assembling. Thanks for the great photos. Best Regards, Kerophile.
Ooooooooooo! That looks good. 8) Thanks for the photo posts Jeff! That's a very interesting application you have there. The #12 is one I've not yet acquired but it sure has a lot of attraction. I really, really like stainless steel. Is the stove a roarer? It certainly looks like that's a roarer plate, but I'm wondering if the perforations in the plate have some sort of quieting effect. Or, actually, what their function might be? Oh! And, is this stove in the pictures burning diesel or kero? Just for fun..... I'm wondering if one of you lucky No.12 owners, Jeff or George, could carefully measure the outside diameter of what I believe to be the vaporization chamber. I'm looking for measurement "X". I'll give it a good think. Be patient with me, please, as it's busy, busy, busy at the moment. Thanks again. Best, Gary
Hello guys! Sorry I meant to say the stove is burning kero. I have yet to try diesel. I agree George about the pump nut is a POS. I used a 24mm flare nut wrench to take it off But I didn't use copper anti-sieze. Great idea... never thought to use it. Thank you. I am not 100% sure what the perforations are for. I will take a night shot tonight and post a picture. I would say it's purpose is to allow more flames to go directly up. Instead of all the flames coming out the side. Not sure. I will try fooling around with it tonight. I will take some measurements right now. Cheers, Jeff
Here is the underside of the roarer plate. Measurement in millimetres As you can see there is a slight rounded corner on the burner. I hope that helps. Thank you Gary for making these wonderful caps!!! Jeff
... per chance could you post a pic of the original burner cap in action ? ... It looks like it could be a stunner.
Sure can! once night falls. in about 8 hours. It is a stunner for sure. Gotta love stainless steel and brass!! Jeff
Hi Jeff and Gary. I tried my No.12 with both a Gary Midi Cap and a No.5 size silent burner this morning. The stove, fitted with a 0.32mm aperture nipple overwhelmed the Midi at low power setting. I then tried a brass Optimus silent outer (no bottom lip) and an inner cap and base plate/spigot made by Gary. This outer cap just fits over the vaporising chamber. This arrangement produced copious yellow flamelets from the burner cap, at all power levels. I believe this is because there is insufficient air being picked up and mixed with the fuel entering the silent caps, resulting in a fuel-rich mixture. The No.12 is a clever burner design, but is basically a flame-plate type, and does pick up additional air in the burner bowl, at higher power settings. The jet is closer to the entrance of the caps, than say on a Op.111 or Primus No.5, so I believe the mixture is fully set, and fuel-rich, when it entered the silent burner in my experiment. Unfortunately I didn't take photos this morning However, here are some archive photos of the Army No.12 performing with its original burner arrangement. These were taken outdoors, in freezing weather, at the beginning of February: They show the stove passing the "Tea Test", and then operating at successively greater power levels: Best Regards, Kerophile.
Thanks for adding the roarer shots Kero!! I am going to try the larger jet tonight. The original jet was made for diesel so I see why the smaller size. Jeff
Hi, Here's my opinion (i.e. not fact ) gained from observation of the operation of the No.12. It's my view that the perforations aid simmering. When operating with the stove turned down to low levels when simmering small flamelets emerge from the perforations. Also, when operating like this there is a distinct difference in the flame plate temperature profile compared to Kerophile's pictures above. In Kerophile's pictures with the stove running at full chat you can see the inner part of the flame plate is not cherry red. However, if you turn the stove right down to simmer, in addition to the small flamelets I mentioned above the middle part of the flame plate goes cherry red and with the small flamelets provides a very slow simmer capability. So maybe the perforations, coupled with the fact thet they are punched out to form deflectors plates (per Jeff's picture of the underside of the flameplate), combine to enhance the simmering abilities. Possibly on simmer part of the flame is deflected by what I've called the defector plates down onto the burner head to maintain the ability to continue to vapourise at low power compared with the flames hitting the skirt and conducting heat back to the burner head when running at higher power? As I said, just conjecture on my part - happy to hear a more scientific explanation. One of my favorite user stoves (cooked a couple of fish fillets on one of mine Saturday evening) that is very controllable across the entire range - from very low simmer right through to full on hooligan mode. Cheers, Graham.
Hello Graham, What you said makes sense to me. To tell you the truth I haven't used the stove that much, new to me. I normally I don't look at the simmering flame. It is a clever design with some well thought out ideas. Have you tried the midi cap on your stove? Best regards and cheers, Jeff
Hi Jeff, BD's silent caps are magnificent. However I don't have any myself. The reason for this is that part of the fun of this stove lark is making stuff like that myself. I have plans for experimenting with making one of my 12s silent but via a different route to a BD cap. However, having been able to do precisely two hours stove stuff since before the solstice I don't see me making any progress before the Autumn - work is manic at the moment which, I guess, I should be grateful for in the current economy. Cheers, Graham.
I hear you about work. They keep asking me if I want to work Sunday . You can imagine my response to that. I look forward to you making a silent No. 12. One problem making one will be fitting it onto the burner. Using the same clips the roarer plate uses I believe would be a great idea. Take care! Jeff
my no 12 runs on coleman with a different burner, i only tried once to run it on diesel and i got loads of sooty smuts and smoke so i must have failed to pre-heat enough. i looked at the original burner and i think the perforations/deflectors on the flame plate are turbulators, similar devices are used on aircraft wings to disrupt laminar airflow and generate turbulence to reduce drag the burner vortex ring demonstrated in previous posts is an example of laminar fluid flow on the brink of becoming turbulent - these little plates disrupt the toroidal vortex and rather than spill round the edge of the burner plate it is broken up to produce the flamelets around the circumference the perforations may not do much in themselves but are just the result of forming the turbulators as simply as possible if this were not the case they would have just punched holes in the burner plate scope here for someone to experiment and gain a better understanding of what is happening this may be the first advance in roarer burner design for a century or more, so there may be other design tweaks waiting to be found
Hi BomX4 and GNE. What you say about the Army No.12 burner and its operation is very thought provoking. Have a look at the plain burner plate shown on Mike's British Army No.12: https://classiccampstoves.com/posts/106667 Is it an earlier version of the plates used on No.12 stoves or did it come from a No.2 stove? It would be good to compare the appearance of the flame with that of the perforated/projecting lug type flame-plate. Best Regards, Kerophile.
Hi All I'm not sure how many folks are still interested in this thread, but here are some more thoughts on the perfs in the plate. I woke up this morning, after pondering the "purpose" of the perforations in the #12 flame plate for several days, with an "answer" in my head. Now, in no way do I claim that the theories that have been advanced are incorrect in total. However, I believe, the main purpose is much simpler. I believe that the perforations are to bend down a circle of "legs" on which the flame plate rests. This establishes an exact distance from the jet to the flame plate and, thus, sets the fuel/air mix at an exact ratio. There are quite a number of posts here at CCS that discuss experimenting with the distance from jet to flame plate on more traditional roarers to get the proper mix. I propose that, bending these "legs" to an exact distance at the factory sets the burner for the "ideal burn". It further eliminates the fussing of users in the field, as there is no need for mods to the plate as it is unlikely that it would be changed due to knocks or bumps during carriage. Photo evidence: The legs may also have side benefits of creating improved turbulence in the flow, etc. Anyway, that's my thought on it. Best, Gary
Hi Gary, interesting theory. Studying your excellent photos indicates thet the flame plate is adequately supported, at the correct height by the four locking lugs. The flame plate is stainless steel, and fairly sturdy, so even if you cut off all the mini-legs (or perforation lugs), the flame plate would still work, albeit without the benefit of flame turbulence. If you look at the photo of the plain flame-plate on Mike's No.12 burner (see link earlier in this thread), it is actually supported by six lugs resting on the top of the burner bowl. If I had access to his stove I would look to see whether there were any locking lugs around the vaporisation chamber at the bottom of the bowl. If there were I might suspect that this type of Army No.2 flame-plate was a later addition to the No.12. Best Regards, Kerophile.
Well, all that may, or may not, be true... My theory is quite a straightforward one. The holes in the top of the burner plate aren't important in themselves because they're just a result of folding down the 16 metal tabs. The height of the burner plate is determined by the four legs and the tabs themselves don't have any other function than to provide 16 gaps through which 16 flamelets emerge. Simple as that... This is, of course, https://en.wikipedia.org/wiki/Occam's_razor in action. It works for me, but obviously YMMV.
